One form of drag racing which has become popular is known as bracket racing. The term “bracket” refers to a window of time that is required for the vehicle to start and complete a prescribed race course, typically a straight quarter mile course. In bracket racing, drag race vehicles are pitted against other such vehicles of generally similar racing abilities because for any given race, vehicles must have race times or alternatively stated, complete the course, in a time interval that is neither less than nor greater than the magnitude of the selected time interval or bracket.
The advantage of this arrangement is that it assures a fairly close race. Otherwise, all other things being equal, the race will be won by that competitor who has devoted more technical resources, and therefore financial resources, to developing a faster race vehicle. Limiting participation of race vehicles to predetermined time brackets both assures a close race, which is of greater interest to spectators, and imposes a limit on otherwise unlimited spending in an effort to become ever faster.
The concept of bracket racing essentially rewards consistency over sheer speed. That is, it becomes desirable to remain within a particular bracket to avoid disqualification in races. At the same time, it is desired to finish the race in an elapsed time period which is the minimum of the predetermined time bracket.
Vehicles for bracket racing have become so developed in their ability to finish races within a particular time bracket that influences such as ambient temperature, humidity, wind speed and direction, and other factors may cause a race vehicle to cover the course too fast and thus be disqualified, or to become slower to the point of being uncompetitive in the selected time bracket. A way of establishing fine control over maximum horsepower would address these problems.
In NASCAR racing, so-called restrictor plates are used to achieve a certain level of parity among race vehicles. While restrictor plates serve their intended purpose in stock car racing situations, they would not be truly useful in bracket constrained drag racing since they are fixed in their levels of control and cannot assure that the race vehicle on which one is placed will actually be limited to any particular elapsed time bracket.
There exists a need in bracket racing to be able to modify engines of race vehicles under closely controlled constraints to enable small adjustments of engine power to suit prevailing conditions in order for a particular race vehicle to qualify for and be competitive within a particular time bracket.